The manufacturers emulsify the lipid soluble propofol in a mixture of water, soy oil and egg lecithin. A wide variety of emulsifiers are used in pharmacy to prepare emulsions such as creams and lotions.Ģ0 ml ampule of 1% propofol emulsion suitable for intravenous injection. This principle is exploited in soap to remove grease for the purpose of cleaning. Detergents are another class of surfactant, and will chemically interact with both oil and water, thus stabilising the interface between oil or water droplets in suspension. Both mayonnaise and hollandaise sauce are oil-in-water emulsions that are stabilized with egg yolk lecithin. In some cases, particles can stabilize emulsions as well through a mechanism called Pickering stabilization. Examples of food emulsifiers are egg yolk (where the main emulsifying chemical is lecithin), honey and mustard, where a variety of chemicals in the mucilage surrounding the seed hull act as emulsifiers proteins and low-molecular weight emulsifiers are common as well. There are three types of emulsion instability: flocculation, where the particles form clumps creaming, where the particles concentrate towards the surface (or bottom, depending on the relative density of the two phases) of the mixture while staying separated and breaking and coalescence where the particles coalesce and form a layer of liquid.Īn emulsifier (also known as an emulgent) is a substance which stabilizes an emulsion, frequently a surfactant. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion tends to imply that both the dispersed and the continuous phase are liquid. Fluid emulsions can also suffer from creaming, the migration of one of the substances to the top of the emulsion under the influence of buoyancy or centripetal force when a centrifuge is used.Įmulsions are part of a more general class of two-phase systems of matter called colloids. This phenomenon is called coalescence, and happens when small droplets recombine to form bigger ones. Homemade oil and vinegar salad dressing is an example of an unstable emulsion that will quickly separate unless shaken continuously. Surface active substances ( surfactants) can increase the kinetic stability of emulsions greatly so that, once formed, the emulsion does not change significantly over years of storage. Over time, emulsions tend to revert to the stable state of oil separated from water. Energy input through shaking, stirring, homogenizers, or spray processes are needed to form an emulsion. Emulsions are unstable and thus do not form spontaneously. Emulsification is the process by which emulsions are prepared.Įmulsion is also a term used in the oil field as untreated well production that consists primarily of crude oil and water.Įmulsions tend to have a cloudy appearance, because the many phase interfaces (the boundary between the phases is called the interface) scatter light that passes through the emulsion. In certain types of magma, globules of liquid NiFe may be dispersed within a continuous phase of liquid silicates. In milk and cream, water surrounds droplets of oil (an oil-in-water emulsion). In butter and margarine, oil surrounds droplets of water (a water-in-oil emulsion). Examples of emulsions include butter and margarine, milk and cream, espresso, mayonnaise, the photo-sensitive side of photographic film, magmas and cutting fluid for metal working.
One substance (the dispersed phase) is dispersed in the other (the continuous phase). Īn emulsion ( IPA: /ɪˈmʌlʃən/ ) is a mixture of two immiscible (unblendable) substances. The surfactant (purple outline) positions itself on the interfaces between Phase II and Phase I, stabilizing the emulsionĮditor-In-Chief: C. The unstable emulsion progressively separates D. An emulsion of Phase II dispersed in Phase I C. Two immiscible liquids, not emulsified B.
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